Kate said she was feeling ‘much better’ as she left hospital (Picture: AFP/Getty)

The Prince of Wales has spoken of his excitement at the prospect of becoming a grandfather, as a pregnant Kate Middleton left the hospital where she was being treated for acute morning sickness by saying she felt ‘much better’.

Kate, wearing a scarf and holding a bunch of yellow flowers, paused to smile for photographers alongside the Duke of Cambridge outside the King Edward VII Hospital in central London before being driven away.

Speaking on HMS Belfast, Prince Charles said he was ‘thrilled’ at Kate’s pregnancy, which was announced earlier this week when she was admitted with hyperemesis gravidarum, a severe form of morning sickness.

‘It’s a very nice thought to become a grandfather in my old age, if I can say so,’ the Prince of Wales said before crossing over to the SA Agulhas, where he was due to meet Sir Ranulph Fiennes ahead of his latest Antarctic exhibition.

‘I’m very glad my daughter-in-law is getting better, thank goodness.’

Over the past four days Kate received fluids and nutrients intravenously, and was also given anti-sickness tablets.

The Prince of Wales said he was thrilled at the news of Kate’s pregnancy (Picture: Getty)

Prince William, also 30, has been by her bedside every day, as have her parents Carole and Michael Middleton, while sister Pippa Middleton and brother James also visited yesterday.

King Edward VII Hospital was forced into an embarrassing apology after two Australian DJs staged a prank call to the hospital posing as the Queen and Prince Charles.

John Lofthouse, the hospital’s chief executive, said managers would be reviewing their telephone protocols after Michael Christian and Mel Greig, who present 2Day FM’s Summer 30 show, were put through to Kate’s duty nurse by reception.

Mr Lofthouse defended his staff members however, saying they were trained to help patients, not ‘cope with journalistic trickery of this sort’.

‘Technically it was a breach of patient confidentiality; having said that the information that was revealed is already in the public domain,’ he added.

Prince Charles made light of the situation earlier today when he asked journalists: ‘How do you know I’m not a radio station?’